1. Field of the Invention
The present invention relates to glutamine-containing compositions and methods for increasing blood flow using the same. Specifically, the present invention relates glutamine-containing compositions and methods for increasing blood flow in the capillary vessels of a subject. The glutamine-containing compositions can be formulated as pharmaceutical products, foods, beverages, animal feed, and the like.
2. Brief Description of the Related Art
Blood enables the transport of oxygen, nutrients, and chemical messengers such as hormones, waste products, and immune cells. Namely, substances are taken up by the blood from the lungs, digestive tract, and endocrine organs, and then they are transported to the entire body via the capillary vessels by the beating heart. Furthermore, waste products and the like are picked up by the blood through the capillary vessels throughout the entire body and finally excreted from the body via the lungs and kidneys, for example. Blood also helps in retaining heat in the body by continuous circulation while at a constant body temperature. Thus, blood flow in the capillary vessels is important for maintaining vital functions, but can be weakened when stresses occur, such as diseases including infectious disease, injury, fatigue, aging, and sudden environmental changes. For example, decreased blood flow in the brain may be related to cerebrovascular dementia and Alzheimer-type dementia, wherein the decreased blood flow causes deterioration of the vital functions (Biomedical Gerontology 2001: 25(2); 83-88). In addition, metabolism by the liver is influenced by the amount of blood flow. Accordingly, it is important to actively increase blood flow under such conditions so that heat retention in the body is increased and substances which actively enhance the vital functions are effectively transported by the increased blood flow.
Agents which have been used to increase blood flow include calcium antagonists, cellular respiration activators, anticonvulsants, in vivo enzymes, and the like.
Some of these agents were originally developed to reduce blood pressure. Such substances are designed to act on the blood vessels in every part of the body so that it is possible to not only increase blood flow in the capillary vessels, but also effect the systemic blood pressure. However, some of these in vivo enzymes, such as kallikrein, also can cause pain, for example. Therefore, it is strongly desirable to develop a method which is effective to increase blood flow and that is safe and easy to use.
It has been previously reported that arginine induces vasodilation. As the mode of action, vascular endothelial cells which contain nitric oxide synthases synthesize nitric oxide from arginine, which causes vasodilation. Externally administered arginine promptly synthesizes nitric oxide, which also produces vasodilation. However, dietary arginine does not usually have the same effect (Folia Pharmacologica Japonica 2002: 119; 7-14).
Although the effects of arginine when ingested have been widely reported, it has been conventionally thought that vasodilation caused by arginine results in an increase in blood flow as well as a lowering of blood pressure. For example, it has been reported, when 30 g or 6 g of arginine was intravenously administered to humans having a body weight of 78 kg on average, the 30 g of arginine lowered blood pressure and vascular resistance, while the 6 g of arginine did not have either effect (British Journal of Clinical Pharmacology 1998; 46: 489-497). In addition, other methods for increasing blood flow using arginine have been reported. In every such case, however, the dosage of arginine is very high, or the arginine must be combined with other compositions which alone act to increase blood flow, such as polyphenols (Anesthesiology 1994; 80: 1320-13, U.S. Patent No. 2002182162 and JP 2004-262878 A). Therefore, increasing blood flow using arginine by itself without concomitant reduction in blood pressure has never been reported.